Draft as of December 16, 2010

YAMATO: Yet Another More Advanced Top-level Ontology
Riichiro Mizoguchi
The Institute of Scientific and Industrial Research
Osaka University
8-1 Mihogaoka, Ibaraki, Osaka 567-0047 Japan
miz@ei.sanken.osaka-u.ac.jp

Abstract
Upper ontology plays a critical role in ontology
development by giving developers a guideline of how toview the target domain. Although some upper ontologies
such as DOLCE, BFO, GFO, SUMO, CYC, etc. arealready developed and extensively used, a careful
examination of them reveals some room for improvement
in a couple of respects. This paper discusses YAMATO1:
Yet Another More Advanced Top-level Ontology which
has been developed intended to cover three features in
Quality description, Representation and Process/Event,respectively, in a better way than existing ontologies.
Keywords: Upper ontology, Ontological engineering,
quality and quantity, informational objects

1

Introduction

Upper ontology is the key of ontology engineering. It playsa critical role in ontology development by giving
developers a guideline of how to view the target domain.
There already exist beautifully designed upper ontologies
such as DOLCE(Guarino 2010), BFO(Smith 2010),
GFO(Herre 2010), SUMO(Pie 2010), CYC(Lenat 2010),
etc. It seems there is no need to develop yet another upper
ontology. However, careful examination of them reveals
some room for improvement in three respects: (1) Quality
and quantity, (2) Ontology of representation, and (3)Distinction between processes and events.
First, quality and quantity need more careful
investigation. One of the most sophisticated property
ontologies is found in DOLCE. It specifies value space foreach quality type under the name of Quality space(region).
A remarkable feature of DOLCE’s conceptualization
about it is the clear distinction between the quality anobject possesses and the quality value(quale/qualia) itself.
This feature is good to support description using <Entity,
Attribute Value> triple2 (referred to as <E, A, V> triple
hereafter) which has been used in knowledge
representation in AI. However, there are other ways ofquality description such as <patient_1, diarrhea>, <cupper,
conductive>, and <rose_1, redness, faint> which seem not
to be covered by DOLCE’s quality ontology. On the other
hand, BFO’s quality ontology has been obtained under the
principle of simple and capturing essentials of quality and

1

YAMATO is the next version of YATO and the namewas suggested by Peter Simons who loves the Japanesebattle ship “Yamato”. Yamato is also the name of theoldest Japanese government.
2
In AI, “Object” is used instead of “Entity”, but to extend
the target things to be described to occurrent, I use“Entity”.

covers only <Entity, Property> type description. As far as I
know, there exist three kinds of data description such as<E, A, V>, <E, P> and <E, P, V> (Egana 2008). However,there is no ontology which supports all these three kinds ofquality descriptions. Even worse, no existing upper
ontology distinguishes between quality in reality andquality description, which causes some confusion whentalking about quality and quantity. The author believes
quality ontology should contribute to facilitation of datainteroperability as well as capturing quality ontologically.
The second aspect is informational object. There are a
lot of informational objects in the world: documents,
books, music, Web pages, etc. They are different fromordinary things in that they have content, that is, they are“content-bearing things”, while cars, tables, dogs, trees arenot. Because representation-related things are classified as
semiotics, it has not been discussed in the philosophicalontology very well. However, we need an ontology of
informational object from the ontological engineering
point of view. Ontology of informational object is
discussed extensively in DOLCE D&S(Gangemi 2003)
and SUMO. Although these ontologies contribute to better
understanding of informational object, there is some room
for improvement. One aspect is the clear differentiation
between representation and representing things together
with its elaboration. For example, while a book as
representing thing is, say, a book you buy at a book store, abook as representation is what the author wrote, that is,something left after subtracting sheets of paper from thebook you buy. It should also be the book in a CD-ROM. In
addition, I believe finer-granular types for talking about
informational object are needed. DOLCE D&S has richconceptualization about representation. It incorporates
situation and concept to realize very comprehensive
ontology of representation. Although it is sophisticated,the framework introduced is a bit too large to deal withordinary informational object such as sentence, music,
plan, etc. Especially, situation is not necessary to talkabout representation. What is more problematic is
introduction of definition of a concept into ontology
because as discussed in 4.1, it violates the principle“Theory should not talk about itself in it”.
The third aspect is most fundamental and is related todifferentiation among objects, processes and events. There
are several views about them. The typical ones are 3Dview and 4D views. BFO nicely reconciles the two viewsby introducing SNAP and SPAN ontologies. GFO is basedon 4D view. DOLCE is based on 3D view. Although
discussion on difference between objects, processes andevents are made in these ontologies, what can change andwhat is an object at all are not very clear. I see both 3D and
4D views of the world are incorrect. I could say the idea ofneither “objects prior to processes” nor “processes prior toobjects” is correct, but both are mutually dependent.
Furthermore, processes can change, though events
cannot(Galton 2009).
This paper discusses a new upper ontology called
YAMATO: Yet Another More Advanced Top-level
Ontology developed to cover the above three issues which
the existing upper ontologies fail to explain satisfactorily.
YAMATO is not fully axiomatized yet, though it should
be done in the near future. It is implemented in Hozo and
OWL and open for use at http://www.ei.sanken.osaka-u.
ac.jp/hozo/onto_library/upperOnto.htm. Some might see
YAMATO is too large and complex. I believe such a
criticism does not apply to YAMATO which tries to reveal
secrets of reality as fine as possible under the condition of
maximization of its utility in practice. Many of the existing
upper ontologies are too simple to explain the reality andto guide domain people to build their ontologies. Whatthey need are not only distinction between objects andqualities but also that between quality and quantity andthat between quality and description of quality, not onlythat between objects and representation but also thatbetween a copy of book and book and that between a novel
and a musical score, and not only that between process andevent but also that between a pulse and a sequence ofpulses and that between to grow and to cut, etc. They alsoneed to know how much similar a procedure and a piece ofmusic are in what sense, why events cannot change while
processes can, etc. YAMATO is designed to answer all theabove questions and the like.

2

Overview of YAMATO

2.1

Basic distinctions

Ontology design is a kind of design activity which
necessarily has some design rationale that largely
influences the resulting ontology. In the case of BFO, it is“representation of reality”, for example. In other words,
any ontology cannot be free from some assumption and/or
designer’s standpoint. The standpoint taken in YAMATO
consists of Newtonian world point of view and 3D-likemodeling, that is, the world is considered as being
composed of the three-dimensional Euclidean space withthe absolute time and both object(continuant) and process(occurrent) exist with equal importance in amutually-dependent manner which is discussed in detail in(Galton 2009). Furthermore, we do not go into micro-level
world in which we need to talk about atoms and/or
particles. By water, I mean amount of water rather than
H2O, since we need to say water is dissective. If we takeH2O into account, it is apparently not dissective. Thispremise is necessary to build a consistent ontology. The
following list includes basic distinctions made in
YAMATO.
(1) Substrate and entity
Space and time are indispensable for things to exist in
the world, while these two can exist independently ofentities. Such independence is essential anddifferentiates the two from entities that inherently
need these two to exist in the real world. Matters areless basic than space and time, but it still is very
substrate-like because every physical individual ismade of/from matter.
(2) Entity and property

Any entity cannot exist without any property, e.g., any
physical object has necessarily a couple of properties(color, mass, size, etc.). At the same time, any
property cannot exist alone. It necessarily needs anindividual to inhere in. Thus, both an individual and aproperty are inherently dependent on each other andcannot be separated. Such a deep mutual
independence is an essential structure of being:
objects vs. processes and matter vs. physical objects
are other examples, though kinds of dependency are
different from each other.
(3) Physical and abstract
We define a physical thing as something which needs
time and space to exist, and introduce semi-abstract
which needs only time to exist. Needless to say, there
is nothing which requires only space to exist. Abstract
things are defined as things that need neither time nor
space.
(4) Continuant(Object) vs. Occurrent(Process3)
This is one of the most controversial issues and has along history of debate. It is sometimes called 3Dmodel vs. 4D model. Common sense is based on 3Dmodel which consists of the 3D Euclidean space withabsolute time. YAMATO is based on a solid theory ofobjects, processes and events, and it deals with themof equal importance (Galton 2009). Furthermore, it
clearly identifies events are made of processes andwhile processes can change, events cannot. We do not
use the term “perdurant” for explaining processes
because it blocks to talk about the difference between
processes and events.
(5) Entity and relation
Relation is sometimes considered as abstract. But it is
not true, though it is something in the higher orderthan an entity, that is, entities first exist and relations
are something found between entities. An example isthe marital-relation with Mr. A and Ms. B that istime-dependent and hence cannot be abstract.
Although it is intangible, it exists in the time frame of
the real world. Friendship between persons, marital
relation, part-whole relation, etc. exist in the world.
People sometimes confuse relation as a formalismwith relation as an existing thing. Typical examples
are action and attribute that are sometimes formalized
as a relation because an action is often formalized as
one between an actor and an object and an attribute as
one between an object and a value. But, of course,
they are not relations ontologically. They are
intrinsically entities included in an ontology.
(6) Informational object vs. non-informational object(Representation and non-representation)
Informational object and symbols are usually dealt
with in semiotics rather than in ontology. However,from the real-world modeling point of view, we needto deal with informational object in our ontology,
since there apparently exist music, novels, texts,
symbols and so on in the real world. Informational
object and non-informational object (object, process,3

Before coming to the discussion on the difference
between processes and events, by the term process, wemean “occurrent”.

(a)
(b)

(c)
(d)

Fig. 1 Top-level categories.

(e)
(f)

relation, attribute, etc.) are very different from eachother. For the informational object, it is not easy toidentify what their instances are. For example, what
an instance of a piece of music is, what an algorithm is,how both are similar ontologically, etc. need somein-depth consideration.

2.2

(h)
(i)
(j)
(k)

Top-level categories

YAMATO adopts single inheritance to make thetaxonomic structure clean like BFO and DOLCE. Using
is-a relation, it is realized in YAMATO that the typehierarchy is made only when the lower type inherits its
intrinsic properties from the super types. Many of themultiple context-dependencies are covered using roles(Mizoguchi 2007). For the cases where genuine multiple
inheritance is necessary, Hozo (Kozaki 2010) prepares
IS-A relation which is nothing to do with identity problem
of instances but only with property inheritance. It isallowed to use only when is-a relation already exists
between the two types of interest. The early version of
YAMATO has been designed under a considerable
influence of Guarino’s upper ontology (Guarino 1995).
is-a relation in YAMATO is something more than usual
property inheritance. That is, it implies inheritance ofidentity criterion, so that when an instance of such a classloses the essential property, then it stops being an instanceof all its super classes. On the other hand, whatever happen
with such properties of an instance that are inherited
through IS-A relation, no influence occurs concerning theidentity of the instance. Note that a type is not a property in
YAMATO. Therefore, human is a type and is not dealt
with as a property. Instead, human type has
properties/qualities such as height, weight, age, etc4.
Fig. 1 shows the top-level categories of YAMATO. At
this level, YAMATO has little significant difference fromother existing ontologies. A more finer-grained view of
YAMATO is shown in Fig. 2 that reveals its features. It
shows a clear distinction between process(a) and event(b).
4(g)

Terminological issues about property and quality is
discussed in 3.2.6 extensively.

(m)
(n)

(l)
(o)

Fig. 2 Detail version of top-level categories.

Concerning ontology of representation, representing
thing(d) is classified under artifact(c), while content(f) andrepresentation(g) are classified under semi-abstract(e)because they need only time to exist. Dependent entity isclassified into generically dependent(h) and specificallydependent(l). The former has quality value(i) as its
subclass which is divided into categorical(j) andquantity(k) and the latter has quality_1(m) as its subclasswhich is divided into and property(n) and genericquality(o). The details are discussed in the following
sections.

3

Quality and Quantity

3.1

Backgrounde-Science needs data exchange world-wide. Especially, inbiology and bio-informatics, data exchange has been
intensively conducted through global collaboration in thedaily activities. In order to make it smooth to exchange
scientific data, the way of description must be compatible
with each other. Description of data/objects is usually
done by determining attribute values. However, quality
description is not well-understood by practitioners. Even

Quality: John’s height of 160cm long
John, John’s height, height, length, 160cm long, 160, cm
Object/human

Associatedwith John

Dependent on
the way ofmeasuring

Quite
generic

lengthnumber Unit/dimension
quantity

Fig. 3 An example of quality.
professionals seem not to agree on the common way ofquality description of objects. This is why in OWL bestpractice WG, there proposed several patterns which would
be useful in many cases of quality description.
As is discussed in (Egana 2008), there are at least three
ways of quality description recommended by BFO,DOLCE and Galen(Alan 2010). BFO recommends<Entity, Property> (e.g., <John, tall>) formalism, while
DOLCE <Entity, Attribute, Value>(e.g., <John, height,
180cm>) and Galen <Entity, Property, Value>(e.g., <John,tallness, large>5). The problem is two fold: (a) one way ofrepresentation is not enough for real world problems
because there exist multiple kinds of quality descriptionsin the real data and (b) there is no explicit model of how
these three are different from and interrelated with eachother. The ontology of Quality and Quantity in YAMATO
tries to give fundamental conceptualization of thoseexisting descriptions in one ontology. To do so, YAMATO
distinguishes between quality in reality and quality
description and has a type hierarchy which reflects
existing notions used in quality descriptions.
Another problem is that there exist several ways of
implementation of a formulation. In OWL, attribute isusually represented in object property. That is, (Entity--attribute--> value) in which attribute is not dealt with asan entity but as a relation. This implementation fails toappropriately represent the growing boy discussed below.
It suggests that not only ontology but tools supporting theontological formulation are also key factors of successful
data description. Note here that Hozo(Kozaki 2010), thetool our group has been developing, is compliant with
YAMATO proposed in this paper.

3.2
3.2.1

3.2.2

An example

See Fig. 3 that shows an example of quality which I
believe many people can agree that it is an example ofquality. The issue here is how to wisely model this quality.
Fig. 3 also shows types and individuals underlying thequality. Among them, “John”, “160” and “cm” have noissue to discuss. Let us briefly investigate characteristicsof the others. Firstly, “John’s height” is something
associated with John and exists at the instance level.
“Height” is generic in the sense that the entity which it isassociated with is unspecified, but is more specific than“length” in the sense that it is dependent on what tomeasure and how. This suggests the notion of “qualityrole” played by length, which is an interesting topic, but it
will be discussed later. The “length” is quite genericbecause it can be height, depth, distance, etc. according to
the context and exists at the class level. Finally, “160cm
long” seems to be quantity and exists at the instance level.
In summary, issues include (1) if “160cm long” is a quality
or a quantity, (2) if an instance of a quality is a quantity ornot, (3) what is “John’s height”?, (4) what is “height”?,
and (5) how is “length” different from “height”? The
following subsections are devoted to answer thesequestions.

As quality,
they share
Same ID

Quality

In quantity space,
they havedifferent ID

The underlying philosophy

One of the contributions of our ideas is clear distinction
between attribute and attribute values. As far as I know,
there are three dependent entities related to the term
attribute: (1) attribute as a type that plays as dimension, (2)attribute as an instance and (3) attribute value that might
correspond to quantity. However, some ontologies do not
distinguish between (2) and (3). In this respect, DOLCE
nicely differentiates instance of attribute from attributevalue by introducing quality for attribute as an instanceand quale/qualia for attribute value. This differentiation
enables us to capture a thing, holding a quantity(qualia),that can change keeping its identity as we discuss it below.
In other words, any quantity exist only one in the world
independently of how many things have those quantities as
their values. We build an ontology for each of
5

attribute(generic quality) and attribute value(quantity)
intended to describe things in terms of the combination of
those dependent entities. We discuss each of the two inturn.

A better example would be <John, diarrhea, severe>.

170cm
160cm

2008

2009

Fig. 4 A growing boy and his height quality.

3.2.3

On change

See Fig. 4 that shows a boy named John who grows. His
height was 160cm in 2008 and 170cm in 2009.
Ontologically, in order to talk about change properly, weneed a non-changing thing keeping its identity during thechange process, otherwise, there cannot exist a change but
just a difference. In the case of growing John, John and hisheight must keep their identities. That is, “John’s height”

must have the same identity at the times of 2008 and 2009.
The values, on the other hand, are 160cm in 2008 and170cm in 2009, respectively, and they have their own
different identity. This analysis reveals that “John’sheight” has something having its identity and it is genericin the sense that its possible values are indefinite.

3.2.4

Quality role

We here discuss the notion of quality role. Many of thequalities people know are not basic quality6 but qualityrole. Let us take an example of height. It is a quality role
whose basic quality is length. In the role theory(Mizoguchi 07), it can be said that “height role is playedby length in the context of a human body”. Height is what
is measured in the direction roughly along the vertical axis
from the ground level to the top. Similarly, depth, widthand distance are quality roles played by length as well. It isjust like a man plays a husband role when he has got
married and like a human plays a teacher role in thecontext of a school. Let us call quality such as length asbasic quality temporarily. Examples of basic qualities
include length, area, mass, temperature, flow rate, voltage,etc. Basic qualities are context-independent andintrinsically represent kinds of quality, and roughly equal
to physical dimensions. Quality roles include height, depth,
input flow rate, maximum weight, area of cross section, etc.
Table 1 shows examples of quality roles.
Table 1 Some quality roles.
Quality roleBasic
quality

Quantity(number +
unit)

age

years

integer + year

heightlengthreal + m

widthlengthreal + m

distance

lengthreal + m

area of crosssectionarea

real + m2

input flow rate

flow rate

real + m3/hour

The notion of quality role satisfies context-dependence
which is one of the most important properties of roles. In
the case of teacher role, a school is its context in whichteacher role is defined. In the case of height, which is aquality role played by length, on the other hand, its context

would be human body, building, etc. with the measuring
manner from the ground level to its top.

3.2.5

Summary of the discussion on quality

A quality must be a certain dependent property possessedby an entity and keeps its identity while its value changes.
In the case of growing John, this understanding suggeststhat not “John’s height of 160cm long” but “John’s height”
should be taken as a quality as shown in Fig. 5. As isalready clear, quality roles are necessarily associated witha particular entity which is the context of them at the
instance level. The fact satisfies the requirement of quality.
Therefore, quality roles are what should be called quality.
Then, “John’s height of 160cm long” would be called
quality instance7 because it is a realization of quality role
“John’s height” at a certain time. In terms of role theory,“John’s height of 160cm long” is called a role holder,which will be explained later, which means a length
playing the “John’s height” role. Then, “height” is called
quality role type which has “John’s height” as its instanceand “length” should be called generic quality type because
it is not associated with any entity yet and specifies whatkind of quality there exist. It was called basic quality in theabove. The results are summarized in Fig. 5. Definitions ofthese basic terms are shown in the following:
1. Generic quality type: The most generic property
which is not yet associated with any particular
context and can play quality role. It represents kindsof property at the class level and its instances
represent concrete values corresponding to quantity
to play quality role: e.g., length, weight, mass, color,area, flow rate, etc.
2. Quality role type: It is a type of property associatedwith a context, and hence is equal to quality role atthe class level. Its instance is played by an instance ofgeneric quality type: e.g., height, depth,(something’s) length, (someone’s) weight, mass ofcross section, input voltage, etc.
3. Quality: It is a property associated with an individual
entity and is a generic name to denote each instanceof quality role type: e.g., John’s height, Tom’s
weight, area of the cross section of this pipe, length of
this pen, etc.
4. Quality instance: A realization of quality: e.g.,
John’s height of 160cm long, Tom’s weight of 50kg,
etc.
These types and their relations are depicted in Fig. 6.

Quality instance: John’s height of 160cm long
John, John’s height, height, length, 160cm long, 160, cm
Object/humanQuality

Qualityrole type

Generic
qualitytype

lengthquantity

numberUnit/dimension

Fig. 5 Informal definitions of quality-related terms.

6This term is temporary and will be renamed as genericquality type later.

7

Although quality realization might be a better name, I
use quality instance to minimize peculiarity.

defined as shown in Fig. 7. In the case of a pen, its lengthrole is played by length. Note here that the term “length”
appears twice in the role name and in the role player name,which is the source of confusion. The former length is a

Examples of relations between these types are shown
below for further clarification:<“John’s height of 160cm long” realization-of “John’sheight”>
Quantity

Quantity (instance)

Generic
quality
type

Sharesame ID

J-height

Quality type

Quality

Quality instanceDifferent ID

Fig. 6 Quality ontology and its use in Hozo (Rectangles with round corners denote instances).
To be definedContext

Role concept

Referring tothe other typeRole player
Role holder
To be definedFig. 7 Hozo legend of role definition [Mizoguchi 2007].
<“John’s height” instance-of height><”height” (role) is-a quality role type><“height” (role) is-played-by length><quality role type is-played-by generic quality type ><length is-a generic quality type><160cm long instance-of length quantity><length quantity is-a quantity>
Fig. 6 also shows two height quality values of John attimes of 2008 and 2009. Although two height quality rolesof John are shown, they share the same identity, while thetwo length quantities, 160cm and 170cm have their own
identities.
I suspect readers would need an explanation about
examples of “(something’s) length” and “(someone’s)
weight”. Before explaining them, however, I need to
explain role theory using Hozo way of representation ofroles (Mizoguchi 2007). Fig. 7 shows Hozo legend of role
definition in which front wheel role is defined in thecontext of bike. It says that a front wheel role of a bikemust be played by a wheel, and front wheel which is awheel playing a front wheel role is called role holder andtype similar to height and depth because it is tightly
associated with its context and the latter length means
one-dimensional extent and is a type similar to area andvoltage. This is why “(something’s) length” is dealt with aquality role type rather than generic quality type. Exactly
the same applies to “(someone’s) weight”, too, that is,“(someone’s) weight” is a quality role played by an
instance of weight as a generic quality type.
Height role holder of human type also needs an
explanation. Height role of human is a type of height roleof John and the former height is a quality role type and thelatter height is a quality. These relationships are consistent
with type-instance relation. On the other hand, however, it
is not clear what is height role holder of human type. It is a
type of J-height role holder of John in Fig. 6. At the sametime, it looks like quality role type as well. Thisasymmetry comes from the nature of roles. We have nospace to discuss this topic in detail, and I would like todiscard what height role holder of human is and to leave
the definitions as they are because height role of humanhas less association with “definite value” than height role
holder of human.

3.2.6

On terminology

There exist similar terms such as property, attribute,quality, quality type, quality role type and quantity. All aredependent entities and cannot exist without an entity withwhich they are associated. It was almost impossible todefine these terms without discussing deep issues related
to them. Because of this difficulty, terms such as attributeand property used thus far should not be taken as technicalterms but as common words which are vaguely defined.
But, now it is the time to differentiate them based on our
discussion thus far. Quality, quality role type and quantity
are already defined with examples. So, the problem is therest two. Therefore, these terms appearing below should betaken as defined here.
Property: As a common term, property is almost asynonym of quality in our context. As a technical term,
however, they are different. The major difference is thatwhile a property can be used as any predicate to any
individual like human(x) or animal(x), quality is used only
for what an entity has. However, considering that our
problem in this paper is to talk about how to
describe/characterize entities, property and quality
become synonym again because there is no necessity fortalking about “human as a property” when describing“human” entity. This definition is only valid in thefollowing sections in this paper, that is, the term property
appearing in the above should not be taken as defined here.
Because we defined quality differently from what isdefined in BFO, by property, I mean “quality” used in
BFO, that is, value combined with its variable or thevariable taking a value that can be possessed by an entity. I
think I need to defend my decision on this. Quality must be
something associated with an entity and can change withkeeping its identity. These characteristics necessarily
derive that quality cannot be something combined with its
value, otherwise, it cannot keep its identity when its value
has changed. Therefore, the notion of quality employed in
BFO is not appropriate in this respect. As was alreadydiscussed, an instance of BFO-defined quality such as“John’s height of 160cm long” is called quality instanceand any length whose value is 160cm is represented as
property in YAMATO, though property is defined mainlyfor qualitative property such as being red, being natural,being artificial, etc..
Attribute: Originally, it is a binary predicate which
relates an entity to its quality instance, e.g., length(pen_1,
10cm). In AI, <E, A, V> is often used to describe entities.
In such cases, “A” stands for quality role type and/or
generic quality type. Following the use of this term in AI,
we could define attribute as a synonym of generic quality
type. However, we intentionally leave this term undefinedfor flexible use in text. So, the term attribute should betaken as a common term in this paper.
In YAMATO implemented in Hozo, the term property
is used to mean BFO’s quality. Because the role hierarchy
is implicit in Hozo, hierarchies of quality and quality role
type are invisible unless Role hierarchy mode of Hozo isused.

Fig. 8 Quantity

3.3
3.3.1

Quantity
What is quantity?

I understand there is a strong temptation to say thatquantity is instance of quality. For example, “1m long”
seems like an instance of length quality. At first glance, it
looks true because it seems simple and natural. However,the facts that quantity must have its own subtype structure
to represent quantized quantity for qualitative values
which should be independent of quality role type and thatquantity has something to say about their instances
independently of their corresponding quality, e.g., “large
is larger than small” and “green is the complement ofred”(Dolce) show it is not appropriate. Quality andquantity must have their own hierarchies to represent theirmutual independence. At the same time, their tight
relationship must be modeled appropriately.
Now, what is quantity? Philosophically speaking,quantity is generically-dependent entity in the sense thatwhile it is not specifically-dependent on any physicalentity, it cannot exist if all physical objects disappear fromthe world. Practically, it is what is denoted by its
measurement. We never know the true quantity ofanything because measurement is always incomplete.
What is correct is that there are two kinds of quantity: true
quantity and its measurement in which the latter is anapproximation of the former. True quantity isunit-independent. A length quantity is independent of how
long 1m is. We will come back to this issue later.

3.3.2

is-a hierarchy of quantity

Quantity has its own hierarchical structure as shown in
Fig. 8. Major features of this quality value hierarchy
include separation of categorical and quantity, andintroduction of qualitative values. By categorical, I mean
genuinecategoricalquality
value
such
as
viviparous/oviparous, colors such as red, blue, green, etc.
Note here that categorical value and qualitative(quantized) value(qualitative quantity) are intrinsicallydifferent. While categories have typicality, qualitativevalues do not. For example, red as a category has the
typical redness at a certain frequency with peripheral
redness at higher and lower frequencies. On the other hand,quantized qualitative values do not have such typical thing
but still have, like quantity, ordinal relationship between
values which categories do not. Quantity is further divided
into quantitative quantity and qualitative quantity. The
former is divided into attribute-neutral andattribute-specific, and the latter includes “large”, “high”,“big”, etc. Examples of attribute-dependent qualitative
quantity include long, heavy, expensive, etc. Quantitative
quantity includes ordinary values such as length quantity,
weight quantity, etc. Large_small is special in the
ontology of quantity. It is introduced to make powerful
qualitative values. Examples include high/low, big/small,etc. One of the well-known issues related to these values is
how to realize qualitative values that are compliant with
“A small elephant is bigger than a big ant” while
guaranteeing “big” is larger than “small” in each context.
Large_small realizes such qualitative values in a
sophisticated way. Details are not discussed here. Those
who are interested in it are encouraged to read the ontology.
This is one of the most remarkable advantages of
YAMATO over existing upper ontologies which cover
only higher level types which are nowadays becoming a
bit obvious.

3.3.3 Confusion about quality as ontology andquality description
Quantity is intrinsically close to description, since it
must be measured to be known by humans and then it must
be described to exist as data about the measured entity.
Without measuring, we cannot talk about particularquantity. This is an aspect of quantity that is tightly
connected to description. However, we have to understandthat quantity is ontologically measurement-independent,
and hence it is unit-independent, that is, length quantity,
for example, can exist as the same quantity independentlyof how long 1m unit is. What is influenced by the size ofthe unit is the measurement result which is a description(representation). Quantity is tightly connected torepresentation in another sense, e.g., a length quantity has
1.
2.
3.
4.
5.
6.
7.
8.
9.
10.
11.
12.
13.
14.
15.

multiple ways of representation depending on which unit
is used among km, m, cm and mm or inch, etc. In
YAMATO, these issues are clearly covered which are notcovered by BFO or DOLCE. YAMATO has ontology ofdata representation as well as ontology of quality
discussed thus far, which is discussed below in 4.3.
There are two kinds of unit: one whose size isstandardized like 1 m and the other one that represents akind of quantity such as length. In YAMATO, the former
is called “The unit” and the latter “unit”.

3.4

Quality and its description

There must be a clear distinction between reality and its
description. That is, <E, A, V>, <E, P> and <E, P, V> arenot reality but quality description of reality. Note here,
however, that these descriptions are also reality in thesense that they exist as data or description just like books
exist. This two-level reality is one of the sources ofconfusion about quality-related issues. Both must be
included in ontology with clear distinction between the
two. As far as the author knows, both BFO and DOLCE
deal only with the primary reality, that is, they do not deal
with quality description. YAMATO would be the first
ontology which takes care of both.
In order to deal with description properly, we first needto establish ontology of description/representation. As
usual, BFO deals with representation (informational
object) only at the highest level. It is called
generically-dependent entity and it is not further
elaborated what they are. The author has once proposed
the ontology of representation(Mizoguchi 2004) which has
not been well-disseminated yet. In this paper, we re-visit
the topic in more detail with some modification of the old
one in Section 4.

3.5

Evaluation and discussion

Examples of several quality descriptions are shown in Fig.
9 in which “(XYZ)” shows the example is the way
recommended by XYZ ontology. These are presented fordemonstrating variety of existing data descriptions andhow well YAMATO can cope with them. Note here that
<E, A, V>-type description is de facto standard in all theengineering data and that <E, P, V>-type descriptions areoften found in clinical domains. These facts strongly
suggest that only BFO or DOLCE cannot cover existing
quality descriptions by itself. As we have discussed above,
all the attributes of an entity are quality roles including
degenerated cases, and hence “A” in <E, A, V> represents

He is tall. (BFO) <E, P1>
He is 185cm high. (BFO) < E, P2>
His height is high/big/large. (DOLCE) < E, A1, V2>
His height is 185cm. (DOLCE): < E, A1, V1>
This rose is red. (BFO) < E, P3>
The color of this rose is red. (DOLCE) < E, A1, V3>
The color of this rose is xyz Hz. (DOLCE) < E, A1, V1_1>
The redness of the color of this rose is high. (Galen) < E, P3, V2>This rose doesn’t have redness. (Galen) < E, P3, V4>
Diarrhea of this patient is severe (Galen) < E, P4, V2>
The length of the pen is short. (DOLCE) < E, A1, V5>
The conductivity of this material is high. < E, A2, V2>
The insulativity of this material is high. < E, A3, V2>This road has many curves. < E, A4, V6> (This road is curvy)
Tom visited Kyoto three times. < E, A5, V7> (He is a frequent traveler)

Fig. 9 Examples of quality description.(See appendix for Ai, Pj, Vk)

only quality role type and do not represent generic quality
type such as length(1D-extent), weight, mass, etc.
Precisely speaking, therefore, the description “(DOLCE)<E, Ai, Vj>” in Fig. 9 should be understood as “DOLCE
supports <E, A, V>-type of description” excluding themeaning of “DOLCE supports Ai”. As shown in Fig. 9,
various quality descriptions are supported by YAMATO.
Among them, descriptions 14 and 15 need special
attention. “many” (curves) and “many times” are qualities
not of “curves” nor of “events”, but of the road and Tom,
respectively.
We formulated the mutual transformation between theabove three kinds of representation. We have conducted
two evaluation experiments of our quality ontology as wellas the transformation. One has been done using
Nanotechnology Index Ontology (NIO) developed by
Yamaguchi, et al.(Yamaguchi 2010) and the other using
clinical observation descriptions. NIO consists of 2,300
concepts in its is-a hierarchy. These concepts are
categorized into 5 categories (Process, Structure, Function,
Material, and Application). In clinical observation, weused all the 3465 observations contained in the master fileof MEDIS(Medis 2010) which is currently used in thedescription of clinical observations in Japanese medical
practice. In both cases, we confirmed our ontology and thetransformation among three kinds of quality descriptions
works quite satisfactorily. In addition, Masuya has been
demonstrating YAMATO’s role of promotinginteroperability for integration of mouse phenotype
databases(Masuya 2009) in which ontology of quality andquantity has been exploited as well as the transformation
formalism among three kinds of quality description.
YAMATO’s ontology of quality and quantity is more
complex than that of BFO and DOLCE. People might
consider this is a drawback of YAMATO. But, it is not thecase. Although they are simple and seem to be right, BFO
and DOLCE deal only with high-level types so that it is notenough to help people capture the reality and cannot
support variety of existing data descriptions by itself.
YAMATO’s ontology of quality and quantity has beenachieved thanks to the power of our role theory. The
differentiation
betweenheightandlength(one-dimensional extent) is beautifully realized byintroducing quality role type which shows that it is tightly
associated with an entity which necessarily differentiatesheight from length(1-D extent) which is not quality.

4

Ontology of informational objects

Ontology of representation (informational object) is badly
needed. Imagine WWW information resources. All ofthem are representations. It would not be a useful ontology
if it does not contain presentation in it. By representation,
we here mean “content-bearing thing”. That is, anythingwhich has content as its essentials rather than itself whichis playing the role of carrier/bearer of the content. A
typical example is a sentence. What exist in WWW, that is,what we can be reached at URLs are not real entities but
representations. Similar to WWW, there exist quite a few
representations in the real world: novel, poem, painting,music, procedure, symbol, etc. What is the instance of arepresentation? How are representations different fromreal-world individuals? These are the questions to answer
in this section. To answer them, we need a sophisticated(a) Representation(b) Representing thing
Fig. 10 Slot structures of representation and representing

Fig. 11 Top-level structure of representation

ontology of representation. What are the instances ofprocedure, music, drama, symbol, calligraphy, painting,poem and novel? Some look easy to answer, but others
might look difficult. Concerning novel, there are threekinds of candidates for its instance: a book of the novel,
the sentences of the novel and their meaning (story).
Concerning the procedure, a document of the proceduredescription, the procedure description, its meaning(sequence of steps) and its execution of those steps are thecandidates. Similarly, a piece of music also has fourcandidates: a musical score book, the musical score, thesound people hear and the playing action which produces
the sound. As the above examples suggest, the source ofthe difficulty in answering these questions is that a
representation has several deeply-related concepts such as
its embodiment, the mode or the form of representationand its content.

4.1

A conceptual model of representation

Before going into discussion on what is representation, let
us share the following principle needed to properly
understand this issue.
Definition of a class is not a representation

An ontology is a theory of being which explains the realworld. Therefore, it exists inherently outside the world andhence the class definition is not an ordinary representation.
It is analogous to the fact that any theory cannot include
itself as an object to explain by itself. It is true that aprocess of an ontology building is a kind of normal process
and the source code representation of the ontology is akind of representation. However, once the representation
is used as an ontology, it goes to the meta-world(outerworld) to explain the real world. This separation is criticalto avoid the common confusion as follows:
A class definition of a concept is a specification of all of
its instances and it is a kind of representation.
Therefore, the relationship between a piece of music
and the sound produced and that between class and its
instance are identical. That is, the former is a
specification representation and the latter is its
realization. Therefore, a piece of music is a class andthe sound you hear is its instance.
Although this line of reasoning looks reasonable at firstglance, it is not appropriate according to the above
observation. It also leads to a difficulty, that is, it implies acomposer designs/generates a class rather than an instance,
which contradicts with common sense that assumes
man-made thing should be an instance. If we would accept
the above observation, as will be clarified below, we
would have to accept that all the individuals such as aprocedure, a piece of music, a plan, a symbol and all the
specifications are not instances but classes.
A representation is composed of two parts, form andcontent shown in Fig. 10(a) like SUMO(Pie 2010). A
representation is not concrete yet as it is. It becomes aphysical individual only when it becomes a representing
thing shown in Fig. 10(b). Top-level structure of
representation is shown in Fig. 11.
This separation is critical. Without this we could not
expect a convincing ontology of representation. We needto realize something exists as content independently of its
representation. Content is the hidden part of representationand it is a proposition which the author of therepresentation would like to convey through therepresentation. Apparently, there can be many ways tocode the same content into different forms to produce
different representations. The identity of “Representation”
is made of both form and content. If their contents aredifferent, then the representations are different.
Concerning things of the same content, the identity isdetermined only by form which is usually what people
sense its existence. When the language is written down on
a sheet of paper, it becomes a representing thing.
Figs. 12 and 13 show is-a hierarchies of representation
form and proposition, respectively. The former is divided
into ordinary form and unit-related form. As is seen by the
subclasses of ordinary form, typical representation form
includes language as a symbol sequence.
Unit-related form is special because it is introduced tocope with quantity as representation discussed in Section 3
and is discussed later intensively. Ordinary form is divided
into symbol sequence and image form, and the latter into
still image and motion image.

Fig. 12 Is-a hierarchy of representation form.

Fig. 13 Is-a hierarchy of proposition

Proposition is what is to be represented and is divided
into representation-primary and representation-secondary.
The latter includes fact, data and thought, etc. By fact, I
mean a happening that a human has recognized and isready for representation to talk about it. The very fact
happening in the real world is an instance of event.
Representation-primary proposition has two subclasses:
designed proposition and product proposition. The former

works as specification of the production of something.
The latter itself is the product. For example, the content ofa piece of music is a specification of the music soundproduced by a music player. Content of a procedure is
specification of the valid sequence of actions. An
execution of the procedure generates a result(product).
Novel cannot be specification of anything because it isalready a product. Note that as will be discussed later,
appreciation of a novel is different from specification
which is common to anything.

4.2

Evaluation and discussion

It is important to clearly distinguish between a
representation and a representing thing. Any
representation is not embodied unless it becomes a
representing thing. A sentence “This is a book” is a
representation in the form of natural language(English)
whose content is the meaning of “This is a book” and what
you see is its printed realization on a sheet of paper which
is a representing thing. Before writing it down, the symbol
sequence “This is a pen” is not a physical individual
because it does not specify what particular icon of symbols
are used to represent each of the symbols. Symbols
without icon are semi-abstract individuals as discussed
below. Note here that “This is a pen” before writing it
down, that is, before becoming a concrete thing is not
something in one’s mind but simply a symbol sequence
independently of where it exists.

4.2.1

On copying

There seem to exist two kinds of “copy” ofrepresentation by symbol: (1) copying the symbol
sequence as a symbol level thing and (2) copying thesymbol sequence as an image(photo-copying).
YAMATO’s representation ontology covers both (1) and(2). Copying of type (1) cannot be done for representation
because any sequence of symbols is unique and isindependent of what concrete icons of letters are used.
That is, there is only one “This is a book” sentence in theworld at the representation form level8. In other words,
contrary to intuition, what you can type-(1)-copy is only
representing thing. In such cases, you can copy it in any
hand-written letters or type it in different fonts and sizes. It
is obvious that type-(2)-copying can be done only for
representing things. In the following, therefore, I use theterm “copy” discarding the distinction between types (1)and (2). The copied stuff is what is on the representation
medium in both cases. Copying is just a generation of thesame representation on a different medium. That is, what
you can copy is not representation but representing thing.
In fact, a novel, say, Tale of Genji, exists in the form of abook. A copy of a book is physically a 3D thing with alogical structure of chapter, section, etc. and with thecontent composed of a representation in terms ofsentences/images. Tale of Genji exists independently of onwhat medium it is written.

8

Do not confuse “This is a pen” as a representation with “This isa pen” as representation form. While the former includes its
content and exist in the world as many as its content denoted by it(representation), the latter is just a symbol sequence.

4.2.2

Identity

Identity of a representation/representing-thing is
divided into four kinds: (0) content level, (1) symbol level,(2) icon level and (3) medium level. Obviously, at thecontent level, two representation/representing-things are
identical iff the contents are identical. At the symbol level,
the identity comes from the representation form, that is,they are identical iff the representation forms are identicalin terms of symbol sequence. At the icon level, they are
identical iff the representation forms are identical in termsof icon level. The medium level applies only torepresenting things, and two representing things are
identical iff they are icon-level identical and their media
are the same as physical individuals. That is, it follows thecommon principle of identity of physical entity. Therefore,
a hand-written copy of a sentence on a sheet of paper is
identical with the original one, at the level (1), iff there isno transcription error. A photocopy of a sentence on asheet of paper is identical, at the level (2), with the original
one iff the photocopying quality is higher than a threshold
and they are always identical with each other in terms ofsymbol level. Concerning medium level identity, there is
only unique representing thing, since copying physicalentities is impossible in principle.

4.2.3

Some examples

Now we are ready to discuss what are procedure, music,
etc. The following lists samples of definitions of some
types and individuals:
Algorithm representation
is-a: Representation
p/o"form": Language
p/o"content": Algorithm
A representation of Quicksort algorithm with C
instance-of: Algorithm representation
p/o"form": <C language>p/o"content": <Quicksort algorithm>
Musical score
is-a: Representation
p/o"form": Musical symbol sequencep/o"content": a piece of music
A score of symphony, the 5th
instance-of: Musical score
p/o"form": <A sequence of musical symbols>
p/o"content": <Symphony, the 5th>
A copy of a book of musical score of the 5th
instance-of: Representing thing
p/o"representation": <A score of symphony, the 5th>p/o"medium": <Pieces of paper>
Sentence
is-a: representation
p/o"form": natural language
p/o: sequence of alphabets
p/o"content": proposition(the meaning)<This is a book> as a sentence
instance-of: Sentence
p/o “form”: <This is a book> as a symbol sequencep/o “content”: <the meaning><This is a book> as a symbol sequence
instance-of: symbol sequence which is-a
representation form
p/o: ”T”,”h”,”i”,”s”,” “,”i”,”s”,” “,”a”,…..

The next problem might be what is the sound(symphony the 5th) people hear? It is an instance ofmusical sound and is a realization of the symphony the 5th,
not an instance of a piece of music which should beconstructed in the hearer’s mind by interpreting thesequence of musical sound and coincide hopefully with thespecification of the piece of music. The playing action isan instance of playing action and at the same time arealization action of the musical sound. Furthermore, therelation between the musical sound and symphony the 5this realization-of relation. Fig. 14 shows an is-a hierarchyof representation.

4.3

Fig. 14 Hierarchy of representation.

<This is a book> as a speech
instance-of: Representing thing
p/o “representation”: <This is a book> as a sentence
p/o “medium”: <a sound><This is a book> as a written sentence
instance-of: representing thing
p/o “representation”: <This is a book> as a sentence
p/o “medium”: <a piece of paper>
The above models declare that an instance of analgorithm is composed of an instance of language
description called form and an instance of proposition
which is a subclass of designed proposition called content.
It can explain various representations, as instances, ofquick sort algorithm by changing the form part which cantake not only the computer languages C, Lisp, Java, etc.
but also the real code in such a language keeping the samecontent, Quicksort algorithm. Note here that an instance ofan algorithm is not a sequence of actions performed
according to the algorithm description but a specificationof valid action sequences. That is, an instance of analgorithm is a specification of its execution. A
specification can virtually exist not as being anembodiment(representing thing), but as the content ofrepresentation. In general, all the designed propositions
are specification of their succeeding realization actions.

Quality representation

As was discussed in Section 3, quality representationmust be dealt with explicitly with careful attention on
distinction between reality and description of reality.
YAMATO introduces tupple, triple and unit-related form
as representation form(Fig. 12), E_A_V, E_P_V, and E_P
as representation of quality, and quantity representation(Fig. 14) for dealing with m, cm, mm, etc. Fig. 15 showsdefinitions of measure, cm length form and cm quantity
representation. Measure somehow transforms the realquantity to its approximation as a representation, that is,
we understand the measurement produces a representation.
In the ontology in Fig. 15, the measurement result isreferred to as quality measurement which is a role holder
and must be an approximation of the real quantity whichshould be unit-independent. Quality measurement(RH) isreferred to in the class constraint of the content slot of cm
quantity representation to represent the measured quantity
in the form of cm. The length representation is referred toas length in cm role holder in the form slot of cm quantity
representation. Cm length form is defined using unit oflength and value slot which stores a number as a valuereferring to 1m unit length as the standard length. It also
defines cm as a role holder which is a new finding on how
to define cm, mm, km, etc. In summary, quantity is madeaccessible as a proposition as a result of measuring. Then,
it is representing in, say, cm quantity representation inwhich length in cm of the quantity is obtained. Thus, aquantity is made an accessible thing as a representation
form in a representation rather than a proposition keeping
the measured quantity in its corresponding proposition.
On the basis of the preparation, a unique type named
equivalence is introduced to explicitly show thecorrespondence between the three ways of quality
descriptions. Although this topic is interesting to discuss,details are omitted in this paper.

5

Objects, Processes and Events

Although this topic is the most philosophical and hence themost important, we here present only the summary of the
discussion as follows because it is in-depth discussed in(Galton 2009):(Excerpt from (Galton 2009)) Any change must be a changeof something. This is already an argument against a ‘pure
process’ view of reality, since we cannot conceive of processes
without their material support. One might ask: what is a person
over and above the sum of its internal processes? But whatmakes this sum worthy of consideration at all is that they
constitute some kind of unity; the unity comes from the fact that
there are other processes, its external processes, which it enacts.

Fig. 15 Measurement and length form.

Thus these questions make the mistake of focusing only on theinternal processes of a person, whereas the external processes
play an essential role in determining the identity of the object.
Hence, rather than trying to characterize an object in terms of its
internal processes (e.g., by identifying the object as the sum of
those processes), we would rather say that an object is a unity
which is what enacts its external processes. We could indeed saythat the object is the interface between its internal and external
processes: it is a point of stability in the world in virtue of which
certain processes are characterized as internal and others as
external. The issue of external vs. internal processes
summarizes as “The water falls, but the waterfall doesn’t fall”.
That is, what a waterfall is doing is not the water falling but
migration upstream as it carves its way into the rock.
Similarly, what a river is doing is not the water flow butchanging the shape of its course of the flow. This is why
we can consider a river is an object which has water flow
as its inner process.
Another important topic is what can change. It is also
summarized as follows(see (Galton 2009) in detail): An
event cannot change. This is not because it is already achange, but because it exists with unity in the temporalspace, that is, it must be always viewed as a whole. Eventsare made of processes. Processes are dissective and hence
they have no unity. It has no whole, and hence it has no(temporal) part. Processes are essentially on-going stuff
and hence they can change. YAMATO is based on thesefindings and has sophisticated upper categories of eventsand processes.
Parts of an occurrent in YAMATO need discussion.
There are two kinds of parts of occurents: temporal partsand causal parts. While the former correspond to
mereological parts of continuant, the latter to functionalparts. Considering that occurrents are things in thetemporal space, the idea of mereological parts isstraightforward, that is, interval-based segmentation for
identifying parts makes sense. However, any process andevent has its causal parts. Imagine, John sneezes while heis walking. The sneezing is nothing to do with his walking
and hence it is not a causal part of his walking. On theother hand, the motion of his legs is essential to his
walking. The alternate motions of his left and right legs arecausal parts of his walking. The bending motions of his
both legs are causal parts of the leg motion. Any causal
part is temporal parts, but, not vice versa.
YAMATO is said to be based on 3D view because it
clearly distinguishes between continuant and occurrent, atthe same time, however, it is said to be based on 4D
because it accepts what exist in the world are occurrents
rather than continuants. It is based on a solid
understanding on what can change and what is an object atall. I could say YAMATO is 3.5D by which, I mean it isbased on the idea of neither “objects prior to processes”
nor “processes prior to objects, but “both are mutuallydependent”.
Events are composed of sub events and all those eventsare constituted by processes as material. Actions whose
operand is anything other than actions are divided into
explicit action and state action. The former represents
actions which imply how to do it, while the latter actions
which mainly imply what state change(what to do) occurs
keeping how to do it implicit. The implications of thisclassification of actions are rich and new. While walk
belongs to the former, move to the latter. YAMATO
distinguishes between arrive as an action and arrival as an
event. As described above, an action is essentiallyon-going stuff, while an event is a unitary whole. An action
exists in an open interval without either end of the timeinterval, while an event exists in a closed interval. So, an
action arrive does not include the very end point.
The separation of what to do and how to do is the very
philosophy of our functional ontology (Kitamura 2006,2010) which provides us with an innovative view ofactions.

6

Roles, functions and relations

Roles are not adequately visible in YAMATO, since it isalready reflected/embedded in Hozo tool. While ordinary
types such as human, table, etc. are defined independentlyof each other, roles are defined within a context which theynecessarily depends on in our role theory (Mizoguchi2007). In fact, roles are used in defining all the types in
YAMATO. These are the reasons why YAMATO does
not have to incorporate roles in it. When one uses Hozowith YAMATO, he/she can enjoy maximally the benefits
offered by both.
Kitamura and I have been intensively involved inbuilding functional ontology for years(Kitamura
2006)(Mizoguchi 2009b). Although we have alreadydeveloped a convincing functional ontology which is

compliant with YAMATO, it is not incorporated into
YAMATO because it is too professional for generalreaders.
Relations are not incorporated in YAMATO neither
because Hozo deals with relations and the wholenessconcepts (ordinary types) in different worlds. Similarly to
Roles, YAMATO implemented in Hozo exploits built-in
and user-defined relations. Hozo has three built-in
relations: is-a, part-of and attribute-of which are exploited
to define types in YAMATO. These are used to introduce
fundamental definitions of types, and user-defined
relations are used to impose semantic constraints amongparts and attributes of a type.

7

Concluding remarks

YAMATO has been implemented in Hozo and is available
at http://www.ei.sanken.osaka-u.ac.jp/hozo/onto_library/
upperOnto.htm with a tool-independent browser. Its OWL
version will be available. It is currently being axiomatizedin the EuJoint project(Borgo 2010). YAMATO was firstbuilt in 1999. Since then, it has been refined and revised
several times. The current version has been extensively
used in several projects such as development of medical
ontology(Kou 2008)(Mizoguchi 2009a), ontology oflearning and instructional theories which is the first
ontology in the community (OMNIBUS), mapping
ontology between PATO and YAMATO (Masuya 2009),
ontology of genomics (GXO (Masuya 2009)), modeling ofmobile users’ behavior(Sasajima 2008), functional
ontology(Kitamura 2006), etc.
As is shown in 3.5 on evaluation, ontology of quality
representation has been well evaluated and its utility has
been demonstrated. Our role theory has been used morethan ten years with Hozo tool, which suggests it has been
already well-established. Ontology of representation is
being used in Genomic ontology, GXO (GXO). Although
the object/process/event ontology is rather new, it iscarefully designed to be compatible with our functional
ontology. The key point is the structure of action whosetaxonomic structure is designed based on device ontology
so that it is clearly differentiated between what is
performed and how it is performed. In summary,
YAMATO, an upper ontology which has appeared at lastafter DOLCE, BFO, GFO, SUMO and CYC, would be a
powerful ontology in the three respects discussed in thispaper. Its full power can be enjoyed when it is used with
Hozo.

Acknowledgement
The author is grateful to my colleagues Yoshinobu
Kitamura, Kouji Kozaki, Munehiko Sasajima and Yusuke
Hayashi for their valuable comments. Special thanks go to
Stefano Borgo for his comments during his work on
axiomatization of YAMATO.

8

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Appendix : Details ofhierarchy shown Fig. 9.

qualityandquantity

property– qualitative property• intrinsically qualitative(P3)– attribute-inclusive(P1)• extrinsically qualitative– attribute-inclusive» being diarrhea(P4)– quantitative property(P2) generic quality (attribute)– intrinsic generic quality• basic generic quality– non-meta generic quality(A1)– meta-generic quality» counting generic quality+ number of objects(A4)+ number of events(A5)• I_O relational– continuous» forward/(A2)» backward(A3)– Accidental generic quality
 quality value– categorical(V3)– quantity• quantitative quantity– singleton» attribute-specific+ ordinary quantity- length quantity(V1)- frequency quantity(V1_1)» attribute-neutral• qualitative quantity– attribute-inependent» binary_value+ non-meta value- quantity quality value(V2)+ meta attribute value- counting_value(V6)- times quality value(V7)– attribute-dependent» length quality value(V5)